No it's a problem with 10.0.3.
I have a 7+ and my wife has a 7 on AT&T. Signal on 10.0.2 was just fine, had no issues. But 10.0.3 just stinks.
At home with AT&T, we live close to a tower, and prior to .3 and also with 9.3.5 on our previous iPhones, we got full bars at our house. But since updating to 10.0.3 we now get 1 bar at our house. I know AT&T didn't change anything with their coverage, it's the iOS update. I am hoping when 10.1 gets released with a new carrier file that it goes back to where it was.
The whole amount of bars vs quality is a bunch of crap. You don't go from FULL bars to ONE in a small update without there being an issue with the update.